G1/S
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Deregulated cell proliferation is the hallmark of cancer, and convergent data from the fields of cell-cycle research and molecular oncology have revealed the key role played by abnormalities of the cell-cycle control genes in multistep tumorigenesis. Along with the p53-mediated DNA damage checkpoint, the G1-governing pathway of D-type cyclins, their partner cyclin-dependent kinases (Cdk), Cdk inhibitors, and the retinoblastoma protein constitute a functional unit and prominent oncogenic target. We have learned a great deal about the molecular basis of G1 phase progression and G1/S transition, their proto-oncogenic defects, and potential clinical significance including diagnostic and prognostic applications and new approaches to gene therapy of cancer.
- MeSH
- biologické modely MeSH
- cyklin-dependentní kinasy antagonisté a inhibitory genetika metabolismus MeSH
- cykliny genetika metabolismus MeSH
- G1 fáze genetika MeSH
- inhibitory enzymů metabolismus MeSH
- lidé MeSH
- nádory genetika metabolismus patologie MeSH
- regulace genové exprese u nádorů MeSH
- retinoblastomový protein metabolismus MeSH
- S fáze genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
CDK12 is a kinase associated with elongating RNA polymerase II (RNAPII) and is frequently mutated in cancer. CDK12 depletion reduces the expression of homologous recombination (HR) DNA repair genes, but comprehensive insight into its target genes and cellular processes is lacking. We use a chemical genetic approach to inhibit analog-sensitive CDK12, and find that CDK12 kinase activity is required for transcription of core DNA replication genes and thus for G1/S progression. RNA-seq and ChIP-seq reveal that CDK12 inhibition triggers an RNAPII processivity defect characterized by a loss of mapped reads from 3'ends of predominantly long, poly(A)-signal-rich genes. CDK12 inhibition does not globally reduce levels of RNAPII-Ser2 phosphorylation. However, individual CDK12-dependent genes show a shift of P-Ser2 peaks into the gene body approximately to the positions where RNAPII occupancy and transcription were lost. Thus, CDK12 catalytic activity represents a novel link between regulation of transcription and cell cycle progression. We propose that DNA replication and HR DNA repair defects as a consequence of CDK12 inactivation underlie the genome instability phenotype observed in many cancers.
- MeSH
- cyklin-dependentní kinasy genetika metabolismus MeSH
- fosforylace MeSH
- HCT116 buňky MeSH
- kontrolní body fáze G1 buněčného cyklu genetika fyziologie MeSH
- lidé MeSH
- oprava DNA genetika fyziologie MeSH
- replikace DNA genetika fyziologie MeSH
- RNA-polymerasa II genetika metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The ability to preserve genomic integrity is a fundamental feature of life. Recent findings regarding the molecular basis of the cell-cycle checkpoint responses of mammalian cells to genotoxic stress have converged into a two-wave concept of the G1 checkpoint, and shed light on the so-far elusive intra-S-phase checkpoint. Rapidly operating cascades that target the Cdc25A phosphatase appear central in both the initiation wave of the G1 checkpoint (preceding the p53-mediated maintenance wave) and the transient intra-S-phase response. Multiple links between defects in the G1/S checkpoints, genomic instability and oncogenesis are emerging, as are new challenges and hopes raised by this knowledge.
- MeSH
- G1 fáze fyziologie MeSH
- myši MeSH
- oocyty fyziologie MeSH
- proteiny buněčného cyklu fyziologie MeSH
- S fáze genetika MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
Embryonic stem cells progress very rapidly through the cell cycle, allowing limited time for cell cycle regulatory circuits that typically function in somatic cells. Mechanisms that inhibit cell cycle progression upon DNA damage are of particular importance, as their malfunction may contribute to the genetic instability observed in human embryonic stem cells (hESCs). In this study, we exposed undifferentiated hESCs to DNA-damaging ultraviolet radiation-C range (UVC) light and examined their progression through the G1/S transition. We show that hESCs irradiated in G1 phase undergo cell cycle arrest before DNA synthesis and exhibit decreased cyclin-dependent kinase two (CDK2) activity. We also show that the phosphatase Cdc25A, which directly activates CDK2, is downregulated in irradiated hESCs through the action of the checkpoint kinases Chk1 and/or Chk2. Importantly, the classical effector of the p53-mediated pathway, protein p21, is not a regulator of G1/S progression in hESCs. Taken together, our data demonstrate that cultured undifferentiated hESCs are capable of preventing entry into S-phase by activating the G1/S checkpoint upon damage to their genetic complement.
- MeSH
- buněčná diferenciace MeSH
- buněčné linie MeSH
- cyklin-dependentní kinasa 2 metabolismus MeSH
- fosfatasy cdc25 metabolismus MeSH
- G1 fáze účinky záření MeSH
- kmenové buňky cytologie metabolismus účinky záření MeSH
- lidé MeSH
- poškození DNA MeSH
- protein-serin-threoninkinasy metabolismus MeSH
- proteinkinasy metabolismus MeSH
- S fáze účinky záření MeSH
- signální transdukce MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The ability to self-replicate is a fundamental feature of life, reflected at the cellular level by a highly regulated process initiated in G1 phase via commitment to a round of DNA replication and cell division. Here we briefly highlight recent advances in understanding the molecular pathways which govern the decision of mammalian somatic cells to enter S phase, and the so-called cell cycle checkpoints which guard the G1/S transition and S phase progression against potentially deleterious effects of genotoxic stress. Particular emphasis is put on the emerging parallel yet cooperative pathways of retinoblastoma protein (pRB)-E2F and Myc, their convergence to control the activity of the cyclin-dependent kinase 2 (Cdk2) at the G1/S boundary, as well as the two waves of checkpoint responses at G1/S: the rapid pathway(s) leading to Cdc25A degradation, and the delayed p53-p21 cascade, both silencing the Cdk2 activity upon DNA damage.
- MeSH
- buněčné dělení MeSH
- cyklin E metabolismus MeSH
- cyklin-dependentní kinasa 2 MeSH
- cyklin-dependentní kinasy metabolismus MeSH
- cykliny metabolismus MeSH
- DNA vazebné proteiny * MeSH
- G1 fáze * MeSH
- inhibitor p21 cyklin-dependentní kinasy MeSH
- kinasy CDC2-CDC28 * MeSH
- nádorový supresorový protein p53 metabolismus MeSH
- nádory genetika patologie MeSH
- poškození DNA * genetika MeSH
- protein-serin-threoninkinasy metabolismus MeSH
- proteiny buněčného cyklu * MeSH
- protoonkogenní proteiny c-myc metabolismus MeSH
- retinoblastomový protein metabolismus MeSH
- S fáze * MeSH
- signální transdukce MeSH
- transkripční faktory E2F MeSH
- transkripční faktory metabolismus MeSH
- transportní proteiny * MeSH
- vazebný protein 1 retinoblastomu MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
The mammalian D-type cyclins D1, D2, and D3 activate the cyclin-dependent kinases CDK4 and CDK6 in G1 and thereby promote the cell's commitment to enter S phase. To elucidate the extent of functional overlap among the D-type cyclins, we have examined several aspects of the least characterized member of this subfamily of G cyclin proteins, cyclin D3. Microinjection of cyclin D3-neutralizing antibody inhibited G1/S transition in human (IMR-90) and rat (R12) diploid fibroblasts, indicating that analogous to cyclins D1 and D2, cyclin D3 is essential for timely progression through G1. In contrast to cyclins D1 and D2, cyclin D3 was (i) ubiquitously expressed among a panel of 70 human cultured cell types; (ii) strongly upregulated upon induction of HL-60 leukaemia cells to differentiate; and (iii) accumulated to high levels in a wide range of quiescent cell types in mouse and human differentiated tissues. Complementary analyses of human biopsies and mouse tissues at different stages of foetal and postnatal development revealed lineage-dependent transient or long-term accumulation of the cyclin D3 protein, correlating with initiation/establishment or maintenance of the mature phenotypes, respectively. Our data support the notion that the biological roles of the individual D-type cyclins are not fully redundant, and suggest a possible dual role for cyclin D3 in cell proliferation and induction and/or maintenance of terminal differentiation.
- MeSH
- akutní promyelocytární leukemie patologie MeSH
- buněčná diferenciace fyziologie MeSH
- buněčné dělení fyziologie MeSH
- buněčné linie MeSH
- cyklin D3 MeSH
- cykliny biosyntéza imunologie fyziologie MeSH
- G1 fáze fyziologie MeSH
- HL-60 buňky MeSH
- interfáze fyziologie MeSH
- kosterní svaly cytologie metabolismus MeSH
- lidé MeSH
- monoklonální protilátky chemie MeSH
- nádorové buňky kultivované MeSH
- orgánová specificita MeSH
- S fáze fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Deregulated cell cycle and defective genome-integrity checkpoints are among the hallmarks of cancer. Here we summarize our recent studies of key components of the GI/S machinery in normal human spermatogenesis, and their abnormalities in testicular germ cell tumours (TGCTs), with special emphasis on carcinoma in situ lesions (CIS). Our combined immunohistochemical and immunoblotting analyses of normal human adult and fetal testes, CIS, seminomas, embryonal carcinomas, and teratomas, revealed an 'unorthodox' spectrum of defects within the so-called RB pathway in TGCTs. The early aberrations included lack of expression of the retinoblastoma tumour suppressor (pRB) and the CDK inhibitor pl9ink4d, and overexpression of cyclin D2. Progression from CIS to invasive TGCTswas associated with loss of another two CDK inhibitors and tumour suppressors: pl6ink4a and pl8ink4c. We also found the lack of pRB and pl9ink4d in fetal gonocytes, the candidate target cell for all types of TGCTs. These findings, together with the status of the Chk2-p53 DNA-integrity checkpoint, are considered in relation to the origin, biology and pathogenesis of TGCTs, and potential implications of the GI/S defects for the curability of these tumours.
- MeSH
- buněčný cyklus MeSH
- cyklin D2 MeSH
- cyklin-dependentní kinasy antagonisté a inhibitory MeSH
- cykliny metabolismus MeSH
- dospělí MeSH
- fosforylace MeSH
- G1 fáze * MeSH
- germinom * etiologie patologie MeSH
- inhibitor p16 cyklin-dependentní kinasy metabolismus MeSH
- inhibitor p18 cyklin-dependentní kinasy MeSH
- inhibitor p19 cyklin-dependentní kinasy MeSH
- inhibitory enzymů metabolismus MeSH
- karcinom in situ etiologie patologie MeSH
- lidé MeSH
- myši knockoutované MeSH
- myši MeSH
- nádorová transformace buněk MeSH
- nádorové supresorové proteiny metabolismus MeSH
- proteiny buněčného cyklu * MeSH
- retinoblastomový protein analýza metabolismus MeSH
- S fáze * MeSH
- spermatogeneze MeSH
- testikulární nádory * etiologie patologie MeSH
- testis embryologie metabolismus MeSH
- zvířata MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- myši MeSH
- zvířata MeSH
A cascade of events is triggered upon the addition of growth factor to quiescent mammalian cells, which ultimately restarts proliferation by inducing the transition from G0/G1 to S-phase. We have studied cyclin D1, a putative G1 cyclin, in normal diploid human fibroblasts. Cyclin D1 accumulated and reached a maximum level before S-phase upon the addition of serum to quiescent cells. The protein was localized to the nucleus, and it disappeared from the nucleus as cells proceeded into S-phase. Microinjection of anti-cyclin D1 antibodies or antisense plasmid prevented cells from entering S-phase, and the kinetics of inhibition showed that cyclin D1 is required at a point in the cell cycle earlier than cyclin A. These results demonstrate that cyclin D1 is a critical target of proliferative signals in G1.
- MeSH
- antisense elementy (genetika) MeSH
- buněčné jádro metabolismus MeSH
- buněčné linie MeSH
- časové faktory MeSH
- cyklin D1 MeSH
- cykliny fyziologie metabolismus MeSH
- DNA biosyntéza MeSH
- fibroblasty cytologie MeSH
- fluorescenční protilátková technika MeSH
- G1 fáze * fyziologie MeSH
- lidé MeSH
- mikroinjekce MeSH
- onkogenní proteiny fyziologie metabolismus MeSH
- plazmidy MeSH
- plíce cytologie fyziologie ultrastruktura MeSH
- S fáze * fyziologie MeSH
- western blotting MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
